1. Field of the Invention
The present invention relates to a unique locking device for use in conjunction with the sealing engagement of a safety valve mechanism, blanking plug device, or the like, within a conduit of a subterranean well.
2. Description of the Prior Art
The prior art is typified by the device as shown in FIG. 1, in which an apparatus 1 has defined at one end thereof a conventional fishing neck 2 for receipt therein of a fishing pin or other device of a running tool (not shown). The apparatus 1 typically has included utilization of a collet mechanism 3 having outwardly protruding finger elements for receipt within a complimentary profile of a landing nipple defining a portion of a well conduit, such as casing or tubing. The fingers of the collet 3 have been permitted to flex inwardly by a probing device carried on the running tool which urges a disc-like plunger device 4 to contact a compressible spring 5 therebelow, whereby affixation of the running tool within the fishing neck 2 causes the probe end to urge the plunger 4 downwardly and away from the fingers of the collet 3 and compress the spring 5. Thereafter, the fingers are enabled to contract inwardly and pass by obstructions defined on the casing or tubing of the well. When the apparatus 1 is located immediate the profile of the landing nipple, the running tool is retrieved from engagement on the fishing neck 2 by conventional means, such as by wire line, whereby the probe is shifted away from contact with the plunger 4 and the spring 5 is enabled to expand and urge the plunger 4 up against the fingers of the collet 3, thereby locking the fingers within the profile.
It can be easily seen that such an apparatus 1 would be deficient by enabling possible improper movement of the plunger 4 interior of the fingers whereby the apparatus 1 may be improperly or inadvertently set in, for example, a profile of the wrong nipple within the conduit or a tubing connection having a similar i.d. as the proper nipple profile. Such improper setting would, of course, not be normally detected until such time as the running tool is retrieved from the well. Consequently, upon discovery of such improper setting of the apparatus 1, the running tool would be required to be re-run into the well for retrieval and/or resetting of the apparatus 1. Obviously, such re-running is costly and time-consuming. Additionally, the construction of such prior art apparatus 1 obviously is not fail-safe, i.e., one is not assured that disengagement of the running tool from the apparatus 1 may be accomplished only after proper setting of the device within the landing or receiving nipple.